Timber Chemistry

Timber Chemistry

an area of knowledge dealing with a chemical industry that uses wood pulp as its raw material. According to the existing classification, the production of rosin and turpentine, as well as industries associated with the thermal decomposition of wood, are considered branches of timber chemistry. Timber-chemistry plants, which combine these manufacturing activities, produce a wide range of products (more than 100 items). The production of cellulose and paper (since the end of the 19th century), and also the hydrolysis industry (in the late 1930’s), became independent branches of the chemical processing of wood.

The thermal decomposition of wood, mainly of broad-leaved varieties, is performed in furnaces and retorts in the absence of air. The main products of decomposition are charcoal, tar water (pyroligneous distillate), and wood resin. Charcoal is used in the chemical industry for the production of activated charcoal and carbon disulfide, in the production of carburizing agents (for surface carbonization of articles from low-carbon steel), and in nonferrous metallurgy (for the production of crystalline silicon). Acetic acid and other materials are extracted from tar water (usually by means of solvents). Acetic acid is purified by rectification and converted mainly into acetate solvents (ethyl acetate, butyl acetate, and so on) and, to a lesser extent (after additional purification), into acetic acid for food. Wood resin is used in the production of an inhibitor for the stabilization of cracking gasolines, a viscosity depressant for clay slurries (drilling mud) used in drilling oil and gas wells, and foundry mold binders.

Rosin is produced from tree sap: resin-impregnated wood, and sulfate soap. Tree sap is obtained by tapping living coniferous trees (mainly pines). The sap is then purified and steam-distilled to remove volatile constituents (turpentine); solid rosin is the residue. Resin-impregnated wood—pine stumps that have become thoroughly permeated by resin—are cut up into chips and the resinous materials are extracted with petroleum ether. The extract is processed to yield rosin and turpentine. “Tall rosin” is produced by decomposition by sulfuric acid of sulfate soap, which is a by-product of cellulose sulfate production and consists of a mixture of the sodium salts of rosin acid and fatty acids, with a trace of neutral materials. The tall oil that forms as a result of decomposition is rectified in a vacuum to yield rosin and tall fatty acids, which are used in the paint and varnish industry. The residue from the rectification is tall pitch. The main demand for rosin comes from the paper, paint and varnish, electrical-engineering, and petrochemical industries (for example, synthetic rubber production), which use about 75 percent of Soviet production. Turpentine is used as a solvent and as a raw material for the production of pinene and camphene and the synthesis of camphor and terpineol.

The main trends in the development of the rosin and turpentine industries are an increase in the production of rosin (mainly of its more economical varieties, extraction and tall rosin) and in the variety of modified and synthetic products derived from rosin (polymerized, hydrogenated, and disproportionated rosin; fortified adhesives for paper; and emulsifiers) and from turpentine.

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